The present invention relates very generally to a method and apparatus for weighing material, and pertains, more particularly, to a method and associated apparatus for separately weighing contributions of material from multiple streams thereof and carrying out this separate weighing using a common scale.
In the printing process, and in other production processes, particularly where a continuous supply of material, such as paper from a roll is fed through a printing press, it is desired to maintain an accurate count of the products from the production process. As long as all of the products from the process are usable, in the case of the printing process, the count is equal to the number of revolutions of the printing press. However, it typically happens that in the course of carrying out the process, some of the products or materials are spoiled for one reason or the other and must be discarded. Thus, the total count of press impressions is no longer a measure of the total count of good product produced. It is and has been thus necessary either to count the good product independently, or to maintain an accurate accounting of the number of products discarded, so that this number can be subtracted from the known total count to obtain an accurate figure for the net "good" count.
A common method for counting "good" products or materials from a printing press is with the use of two counters. One of these is a gross counter which counts every revolution of the press whether a "good" product is produced or whether the product is to be discarded. The other counter is a net counter. The net counter can be turned on and off by the press operator, in accordance with whether he thinks the copies being made are acceptable or not. The problem with this technique is that it is subject to error as the operator may be unaware that the press has started to produce copies that should be discarded and therefore the operator may fail to set the counter. It is typical that when the defect is discovered, that the operator may estimate the number in order to prevent the necessity of restarting the net counter when good copies are again produced.
To overcome the aforementioned problem, ratio scales have been employed to measure the number of signatures (impressions or sheets in the case of paper) discarded. The number so determined is subtracted from the gross count to obtain a more accurate net count. Alternatively, when the number of signatures discarded is determined from the ratio scale, this may be added to the required number of "good" counts in order to determine the gross counter reading at which the press is to be stopped. Although this technique is somewhat of an improvement, it is still subject to human error because of the bookkeeping involved. Also, because one printing press typically produces up to four different products at one time, the bookkeeping becomes particularly complicated. Also, the bookkeeping or record keeping is complicated by virtue of the fact that usually only one scale is used to measure the waste paper from several deliveries of the same press.
Another technique that is employed involves the use of separate scales for each product. However, this technique requires substantial floor space and is also very expensive to implement. Still another common technique is to employ one scale but with multiple operator buttons such as four operator buttons to allow the press man to enter which printing stream the last weight came from. This technique require too much operator involvement and slows the process since several people may be depositing sheets at one time. A variation of these techniques uses a small scale or scales to weight the individual bundles before they are deposited in the central bin. This variation has all the above-mentioned problems and further requires an extra step.
Accordingly, it is an object of the present invention to provide a method and associated apparatus for separately weighing contributions of material, typically in sheet form from a printing press, from multiple streams thereof, and providing this weighing with a common scale. Another object of this invention is to provide an apparatus for registering accurate "good" counts from each of multiple press deliveries using a common scale.
A further object of the present invention is to provide an improved method and apparatus for weighing material in accordance with the objects and in which the method is carried out without the need for manual record keeping or manual entry of data.
Still another object of the present invention is to provide an improved method and associated apparatus for weighing materials from multiple streams with a common scale and wherein the apparatus is safe to operate, jam proof, accurate in operation, and easy to maintain.
To accomplish the foregoing and other objects of this invention there is provided in accordance with one aspect thereof, apparatus for weighing material from multiple streams with a common scale, which apparatus comprises a plurality of separate means, each for temporary storage of a quantity of said material that is to be weighed. In the embodiment described herein, the material may be in the form of paper used in a printing process and the weighing is of spoiled product. The apparatus of the present invention is for use with a single common scale and yet provides for a total count of waste material for each of the plurality of storage means. In addition to the plurality of separate means for this temporary storage of the material and the common scale means, the apparatus also comprises means for sequentially releasing the material from the respective separate means for storing so as to enable delivery thereof to the common scale means. This is typically carried out with the use of a common storage bin associated with the scale means. Electronic means is used for control and includes means responsive to the scale reading for sensing increments in scale weight for each respective release of material. The electronic circuitry has to determine with which of the deliveries the weight increment corresponds. Thus, there is provided a means for totaling the respectively sensed weight increments to provide a plurality of separate counts corresponding to weight and associated with each of the respective means for storage. In accordance with the invention the storage means may comprise a hopper and the means for releasing may be constructed in combination with the storage means in one of two preferred forms described herein. This may comprise either a metered discharge which may be in the form of a gate cover or moving aperture arranged to open at the time of discharge and to be closed at all other times. The delayed transport technique may comprise a conveyor used to carry the material towards the discharge opening. When the conveyor is operated it will discharge the material upon it into the waste bin below. When it is stopped, it will store material for the next discharge cycle. The means for sensing increments in scale weight may comprise a difference means or a difference circuit having an output count or magnitude corresponding to the difference in weight between a present scale weight and the next scale weight after operation of the means for releasing. Preferably, means are provided for converting the weight factor sensed to a count that corresponds to the number of pieces of material released in a batch. The means for totalling substantially adds counts corresponding to weight and displays a count indicating total pieces weighed per stream.
In accordance with another aspect of the present invention, there is provided a method of weighing material from multiple streams with a common scale. This method comprises the steps of separately and temporarily storing a quantity of the material that is to be weighed from each respective stream and sequentially and mutually exclusively releasing the material from its temporary storage to the scale. The next step is that of sequentially sensing increments in scale weight for each respective release of material. Finally, each of these increments corresponding to a predetermined stream is added so as to accumulate sensed weight increments associated with each respective stream.